Worms in an aquatic sample

Curious about what microbes might be found in the water that accumulates in the container below potted plants, I took some samples in a test tube. What I then found out were a large number of white-colored worms wriggling in the water. These were less about 5mm in length.

At first I assumed these might be larva of some mosquito species. However, their larva are generally tend to move and attach to the surface of water. However these worms would swim comfortably in the water deeper into the test tube.

I took a sample having one of these worms and mounted it on a cavity slide. Observed at 140x magnification.